[Sorption and degradation of 17beta-estradiol to anoxic activated sludge]

Batch experiments were conducted to investigate the sorption isotherms and degradation kinetics of 17beta-estradiol (E2) at a low levels (microg/L) by anoxic activated sludge. The effects of temperatures and the concentrations of electron acceptor on the sorption and degradation were also investigated. Results showed that, when the initial concentrations of E2 were 5-15 microg/L, E2 was completely degraded after 2 h under anoxic conditions. Anoxic degradation of E2 in the activated sludge can be described by first-order reaction kinetics. During degradation, E2 sorption was well correlated by both Freundlich and linear adsorption isothermal model at different temperatures. The biodegradation behavior was inside the sludge phase. The transfer of the compound between the water phase and the sludge phase followed a linear adsorption isotherm. Temperature exerted significant effects on both the sorption and degradation of E2. The increase of temperature enhanced the E2 biodegradation rate but decreased E2 adsorption capacity on the sludge. The first-order reaction constants for E2 anoxic degradation at the temperatures of 10, 20 and 30 degrees C were 2.411, 3.045, and 3.527 h(-1), respectively. The distribution coefficients (k(d)) were 540.9, 460.4, 396.9 L/kg for 10, 20, 30 degrees C, respectively. To some extent, the first-order rate constant of E2 anoxic degradation was infected by NO3-; -N concentration (10-30 mg/L).